Paradoxical memory occurs when an individual, asked to remember an experience, produces or recognizes an event that was not experienced but is consistent with the structure of what has been experienced. It involves losing specific autobiographical information and retaining instead a schema or set of principles that reflect an understanding or model of the experience. Several recent studies in which subjects were instructed to remember accurately have demonstrated paradoxical memory, suggesting that it can be used to assess the construction of mental models. The proposed experiments use paradoxical memory to investigate the role of constructive processes in the acquisition of knowledge. Subjects will be asked to learn a set of sentences that describe a structured state of affairs such as the results of tennis matches among eight players or the sequence of symptoms experienced by people who die of a strange new disease. Specific experiments will be devoted to the effects on constructive memory of the following conditions: (a) Explicit instructions for the subject to look for a system or pattern while learning, (b) Implicit instructions created by the background information and the subject matter of the sentences, (c) The order of presentation of the sentences, and (d) The structural ambiguity of materials that can be represented by two different models. It is argued that the knowledge possessed by individuals is in the form of systematic mental representations that resemble informal scientific theories in logical structure. These mental models form the basis of the entire spectrum of individuals' knowledge, including their knowledge of academic subjects, work-related activities, recreational pursuits, and the pattern of social interactions that include them as participants. The ultimate goal of the studies outlined is to describe and understand how these mental models are built up for experience and to determine what conditions enhance or inhibit the constructive processes involved.